I noticed on the linux-xfs list an announcement by Steve Lord where he listed a few things which might make it into XFS in the next few months:
http://oss.sgi.com/projects/xfs/mail_archive/200305/msg00233.html
One of them, "Mixed case support in XFS (for Samba)" presumably means case-insensitive filenames/directories. Keith Owens also mentioned the lufs (Linux userland fs) project at http://lufs.sf.net/
This apparently allows for case-insensitive filesystems by way of a userspace wrapper. For anyone who might be having trouble with case-sensitive UNIX filesystems, these might be worth considering.
Note that I haven't tried lufs, and the XFS stuff hasn't yet been released, but maybe the information is useful to someone.